US2656062A - Pallet gripping device - Google Patents

Description

Oct. 20, 1953 J. B. THOMAS 2,656,062

PALLET GRIPPING DEVICE Filed March 28, 1950 3 Sheets-Sheet l INVENTOR.

J. B. THOMAS BY ATTORNEY Oct. 20, 1953 J. B. THOMAS PALLET GRIPPING DEVICE Filed March 28, 1950 s Sheets-Sheet 2 Oct. 20, 1953 J. B. THOMAS 2,656,062

PALLET GRIPPING DEVICE Filed March 28, 1950 s Sheets-Sheet :s

INVENTOR. J. B. THOMAS Patented Oct. 20, 1953 UNITED STATE EY ENT OFFICE This invention rel-ates to material and article handling and more particularly to a pallet gripper for retaining a load carrying pallet on an industrial truck while the load is removed therefrom.

Heretofore numerous devices for retaining a pallet in position on an industrial truck have been proposed but many of these have provided no means for automatically centering the device with relation to the pallet thus requiring extremely accurate and careful manipulation by the operator and others have required rather extensive modifications of the pallet structure including the provision of teeth thereon to be engaged by laws on the truck.

It is therefore an object of this invention to provide a pallet gripper of economical construction which is designed to utilize a source of hydraulic power already provided on an industrial truck or a separate source of power provided for the purpose of actuating the gripper.

It is a further object of the invention to provide a pallet gripping device for application to an industrial truck having a pallet stack unloader thereon and which is designed to grip and hold the pallet against movement relative to the truck while the load or stack is removed therefrom.

It is a further object of the invention to provide a pallet gripping means which will automatically grip the pallet even though the same is appreciably out of alignment with the pallet engaging means carried by a conventional industrial truck.

It is a further object of the invention to provide a pallet gripping means for application to a conventional industrial truck in conjunction with a pallet stack unloaded in which the unloader and gripping means may be conveniently operated from a common source of hydraulic or pneumatic power and in which operation of the pallet gripper is of necessity initiated prior to operation of the stack unloader.

It is a further object of the invention to provide a pallet gripper of relatively simple and economical construction in which the parts requiring accurate machine work have been held to a minimum and which will automatically accommodate for irregularities in the pallet and misalignment thereof with an industrial truck to which the pallet gripper is attached.

Further objects and advantages of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a view in perspective showing the pallet gripper of this invention and a pallet stack unloader' attached to a conventional industrial fork truck; the latter being shown in phantom.

Fig. 2, a view in perspective of the pallet gripper apart from the truck to which it is normally applied;

Fig. 3, a fragmentary plan view with parts in section for greater clarity showing the pallet gripper of this invention attached to a conventional industrial truck;

Fig. 4 a sectional view on the line 4--4 of Fig. 3 of the pallet gripper forming this inventionand showing the device applied to a conventional 5 industrial truck;

Fig. 5, a fragmentary side elevational View showing the pallet gripper applied to a conventional industrial truck; and

Fig. 6, a diagrammatic view of the hydraulic power circuit utilized in connection with a pallet stack unloaded and the pallet gripper of this invention.

With continued reference to the drawing there is shown in Fig. 1 a conventional industrial fork truck it! having ground engaging wheels I l and steering mechanism [2. Truck I 0 is provided with the conventional pallet or load engaging fork arms I 3 which may be secured to an elevating mechanism [4 for raising and lowering a load carried by the arms 13.

Since it is frequently desirable to unload the merchandise carried by a pallet as a single unit the truck ii) is also provided with a pusher mechanism indicated generally at l5 and since this pusher mechanism comprises no part of the instant invention the structure thereof will only be briefly described. Uprights l6 connected by cross bars I1 and 18 are secured to the elevating mechanism i4 and move upwardly and downwardly with the load carrying arms I3. Secured to the uprights I5 are operating cylinders I? which may receive hydraulic or pneumatic power from a source provided on the truck It or from a separate motor driven pump mounted on the pusher mechanism [5. Pistons 2c are sliclably received in cylinders l9 and these pistons connect with a linkage mechanism 21 which is secured to a grille-like load; engaging pusher member 22. Movement of the pistons 20 outwardly of the cylinders l9 serves to move the pusher member 22 forwardly and eject a load carried by a pallet supported on the arms E3 or a load directly carried by the arms l3. Movement of the pistons 20 inwardly of the cylinders i'9' retracts the load engaging member 22 to a 001- lapsed position whereby the arms 13 may engage a pallet or a load over substantially the entire length thereof since the space occupied by the pusher mechanism l when in collapsed condition is substantially negligible.

It has been found in practice that it is frequently necessary to provide some means for retaining a load carrying pallet on the arms !3 when the load is ejected from the pallet since if such holding mechanism were not employed very often the pallet as well as the load is removed from the truck. For this purpose a pallet gripping mechanism indicated generally at 23 is secured to the arms 53 or elevating mechanism l4 in any suitable manner. As best shown in Fig. 2 the pallet gripping mechanism 23 comprises a pair of cylinders 24 and 25 which are substantially coextensive and are disposed in parallel relationship, cylinders 24 and 25 being secured together adjacent their ends by blocks 26 and 27, these blocks being provided with screw threaded apertures or the like 28 and 29 to facilitate attachment of the pusher mechanism 23 to the arms 13 or elevating mechanism l4. Obviously, any desired method of attachment may be employed, it only being necessary that the pusher mechanism 23 be rigidly secured in place and that any relative movement between cylinders 24 and 25 be prevented.

Pallet gripping shoes 33 and 3| are pivotally mounted by screw threaded fastening means or the like 32 and 33 on forwardly extending arms 34 and 35 which in turn are secured to blocks 36 and 31, slidably received on the cylinders 24 and 25. Block 35 is provided with fluid pressure connection nipples 33 and 39 and block 3i is provided with fluid pressure connection nipples 40 and 4!.

The specific structural details of the pusher mechanism 23 are best shown in Figs. 3 and 4, there being a doubled ended piston 42 slidably disposed on cylinder 24 and an identical piston 43 slidably disposed in cylinder 25. As best shown in Fig. 4 piston 43 is provided with a bore 44 at the left-hand end thereof and a bore 45 at the right-hand end, these bores terminating short of the longitudinal center of the piston in order to form a dividing wall 46. Bores 44 and 45 are open at each end of the piston and adjacent each end there is provided grooves 47 and 48 for receiving sealing rings 49 and 59 of any desired character. Sealing rings 49 and 50 engage the inner wall of the cylinder 25 and serve to prevent leakage of pressure fluid between the piston 43 and the Wall of the cylinder.

Partition 46 is provided with a recess 5| for receiving a block 52 which projects through and is slidably received in a slot 54 provided in the wall of the cylinder 25. A similar slot 53 is provided in the wall of the cylinder 24. Partition 4B is also provided with bores 55 and 56 communicating with the bores 44 and 45, respectively, in each end of the piston 43. The block 5i is secured in position by threaded nipples 33 and 39, these nipples being received in apertures in the block 52 and threadedly engaging apertures in the partition 45. Nipples 38 and 39, respectively, provide means for introducing and relieving fluid pressure in the bores 44 and 45 and consequently in each end of the cylinder 25. Block 52 also serves to secure the block 38 to the piston 43 thereby preventing relative movement therebetween and causing the block 36, arm 34 and pallet engaging shoe 36 to move therewith upon movement of the piston 43 in either direction. The cylinder 24 is closed at each end by caps 58 and the cylinder 25 by caps 59. The nipples 38 and 4! are connected by a flexible conduit 8% provided with a T-fltting 3! for connection to a control valve and source of fluid pressure. Likewise nipples 33 and 40 are connected by a flexible conduit 32 provided with a T-fitting 63 to be connected to a control valve and source of fluid pressure. In certain installations it may be desirable to introduce fluid pressure to the cylinders 24 and 25 at each end there of in which case suitable fittings to receive the conduits 38 and 62 would be provided on the caps 58 and 59.

The pallet gripping shoes 34 and 3i as best shown in Fig. 3 each comprise a channel shaped body 34 received over arms 34 and 35 pivotally secured thereto by a screw threaded fastening means or the like 32 and 33, the body t4 being covered on the gripping face thereof with a cushioning element 65 of rubber or other suitable material. Element 35 may be secured to the body 34 by screw threaded fastening means or the like 66 or if desired may be bonded thereto by any Wellknown process. The gripping shoes 32) and 3| are normally biased to the position shown at the right in Fig. 3 by a spring or other equivalent means 67 secured to the arm 35 by screw threaded fastening means or the like 68, spring 6'? normally bearing against a flat surface E9 on the interior of the body 64. The biased position of pallet gripping shoes 33 and 3! facilitates the engagement thereof with the pallet particularly when the pallet and truck it: are somewhat out of alignment.

Since it is desirable that the pallet gripping means of this invention operate in conjunction with and timed relation to the pusher means it there is shown diagrammatically in Fig. 6 a fluid pressure circuit whereby such operation may be accomplished. A fluid reservoir 7!] may be provided on the truck It or any other desirable location, reservoir lii being connected through a strainer or other suitable filter H with a fluid pressure pump l2 driven by a motor 13. Pump '32 is connected through a suitable fitting 14 with a solenoid operated control valve 75. Also connected to fitting i4 is a relief valve 16 with the outlet Tl thereof connected to a return conduit l3 discharging into the reservoir '16. Ihe relief valve 16 is provided as a safety measure in order to relieve any excessive pressures which may develop in the system. Upon actuation of the solenoid valve 75 to operate the pusher I5 fluid pressure flows through conduit 19 to a sequential bypass valve Sil and thereafter through conduits 8i and 82 to the pusher operating cylinders l9. The opposite ends of cylinders H! are connected through conduits S3 and 34 to a conduit also connected to solenoid valve i5. During the unloading operation of the pusher i5 conduits 33, 84 and 85 serve as discharge lines for the cylinders M3, the fluid therein flowing through the valve 75 and conduit '18 to reservoir 59.

Conduit 53 leading from valve i5 is connected to the sequential by-pass valve 86 and a conduit 36 which in turn is connected to T-fitting E3 and flexible conduit 42 leading to the pistons 42 and 43 disposed in cylinders 24 and 25. Conduit 85 is connected through a conduit 8! with T-frtting 6i and flexible conduit 33 which is also connected to pistons 42 and 43 disposed in cylinders 24 and 25. While the valve 75 has been described as solenoid operated, obviously if desired, this valve could be operated manually or by any other suitable mechamsm.

In operation since it is desirable that the pallet gripping means 23 securely engage the load carrying pallet prior to operation of the pusher mechanism 15 means has been provided in the form of the sequential by-pass valve ac to insure that such sequential or timed operation takes place. Upon actuation of the solenoid valve 15 to introduce fluid pressure from pump 72 to conduit 19 this fluid is prevented from flowing to conduits 8i and B2 communicating with pusher operating cylinders ill by the sequential bypass valve 89 until sufficient pressure has built up in the conduit 19 to operate and open bypass valve 38. Con,- sequently the initial fluid pressure will be conducted through conduit 86, T-fitting 63 and conduit 62. From conduit 62 the fluid flows through bores 55 and bores 44 in pistons 42 and 43 thus urging these pistons, blocks 36 and 31, arms 34 and 35 and pallet engaging shoes 39 and 3| carried thereby inwardly toward each other to grip a portion of the pallet or other object therebetween. The flow of fluid through conduit 86 will continue until the pallet gripping shoes 30 and 3| have engaged the pallet with suflicient force to hold the same, this action resulting in an increased pressure in the conduit i9 and upon this pressure reaching a predetermined value the sequential bypass valve 86 will open and permit the flow oi fluid to conduits 8i and 82 and pusher operating cylinders 19 whereupon the pusher mechanism l5 will be operated to move the load from the pallet. Upon completion of the unloading operation the solenoid valve '55 is operated to introduce fluid pressure through conduit 85 to conduits 83 and 84 and pusher cylinders [9, thus retracting the pusher mechanism. At the same time this fluid pressure will flow through conduit 81, T-fltting 8i and conduit 60 to the opposite ends of gripper operating pistons 42 and 43 to move the pallet gripping shoes 30 and 3| away from each other and release the pallet.

In the operation of industrial fork trucks it requires considerable skill on the part of the operator to accurately align the pallet engaging forks or arms with the pallet and this difliculty is materially increased where it is necessary to accurately align pallet gripping jaws with cooperating means on the pallet and consequently the pallet gripping structure above described has been designed to automatically center itself with relation to the pallet and to grip the same even though the truck and the pallet are considerably out of alignment.

The operation of the pallet gripping mechanism to grip a cooperating portion of a pallet positioned considerably to one side of the center line between the pallet gripping shoes 39 and 3| is best shown in Fig. 3 in which there is disclosed in phantom at 88 a longitudinal reinforcing member normally provided on the underside of a load carrying pallet centrally thereof. As shown in Fig. 3, member 88 is positioned closely adjacent the lefthand pallet gripping shoe 38 with the righthand gripping shoe 3| considerably spaced therefrom. Upon the application of fluid pressure to the pistons 42 and 43 to move the pallet gripping shoes toward each other the piston 43 carryin pallet gripping shoe 30 will move toward the right as viewed in Fig. 3 until it contacts member 88 at which time movement of the gripping shoe 39 toward the right will cease and gripping shoe 3| will continue to move toward the left until it engages and grips the member 83. This action is due to the fact that the fluid pressure which actuates pistons 42 and 43 to provide a gripping action is carried thereto from a common source and since in accordance with the well known law that fluid pressure in a closed space will be transmitted with equal intensity in all directions the gripping shoes 30 and 3| will automatically center themselves with relation to the member 83. It is, therefore, only necessary for the operator of the truck to po sition the same in such a manner that the arms I3 will engage beneath the pallet to be raised and upon actuation of the proper controls the pallet gripping shoes automatically grip the pallet and at the same time compensate for any misalignment between the truck and the pallet.

It will be seen that by the above invention there has been provided a relatively inexpensive and highly efiicient pallet gripping mechanism which may be conveniently applied to conventional fork trucks without material modification thereof and which may operate in conjunction with a load pusher installed thereon, the power for operating the pusher and gripping means being supplied either from a source on the truck or from a self-contained pressure producing unit.

It will be obvious to those sldlled in the art that various changes may be made in this invention without departing from the spirit and scope thereof and therefore this invention is not limited by that which is shown in the drawing or described in the specification but only as indicated in the appended claims.

What is claimed is:

1. For use with an industrial fork truck for transporting load carrying pallets and having a fluid pressure operated pallet unloader, a pallet gripping device comprising spaced parallel cylinders secured to said truck, a double ended hollow piston slidably disposed in each cylinder, each piston having a partition at substantially the midpoint thereof, a flexible fluid pressure conduit connecting the hollow outer ends of each piston, a second flexible fluid pressure conduit connecting the hollow inner ends of each piston, right and lefthand blocks slidably mounted on said cylinders, said righthand block being se-' cured to one piston for movement therewith, said lefthand block being secured to the other piston. for movement therewith, right and lefthand pallet gripping shoes pivotally carried by said blocks, means to bias said shoes in one direction and a fluid pressure source and control means connected to said unloader and said flexible conduits whereby upon actuation of said control means said gripping shoes will move toward each other to grip said pallet and automatically compensate for any misalignment between said pallet and said truck and thereafter said unloader will operate to remove the load from the pallet.

2. For use with an industrial fork truckv for transporting load carrying pallets and having a fluid pressure operated pallet unloader, a pallet gripping device comprising spaced parallel cylinders secured to said truck, a double ended hollow piston slidably disposed in each cylinder, each piston having a partition therein, a flexible fluid pressure conduit connecting the hollow outer ends of each piston, a second flexible fluid pressure conduit connecting the hollow inner ends of each piston, right and Iefthand blocks slidably mounted on said cylinders, said righthand block being secured to one piston for movement therewith, said lefthand block being secured to the other piston for movement therewith, right and lefthand pallet gripping shoespivotally carried by said blocks, means to bias said shoes in one direction and a fluid pressure source and control means connected to said unloader and said flexible conduits whereby upon actuation of said control means said gripping shoes will move toward each other to grip said pallet and automatically compensate for any misalignment between said pallet and said truck and thereafter said unloader will operate to remove the load from the pallet.

3. For use with an industrial fork truck for transporting load carrying pallets and having a fluid pressure operated pallet unloader, a pallet gripping device comprising spaced parallel cylinders secured to said truck, a double ended hollow piston slidably disposed in each cylinder, each piston having a partition therein, a flexible fluid pressure conduit connecting the hollow outer ends or" each piston, a second flexible pressure fluid conduit connecting the hollow inner ends of each piston, means connected to each piston and carrying right and leithand pallet gripping shoes, means to bias said shoes in one direction and a fluid pressure source and control means connected to said unloader and said flexible conduits whereby upon actuation of said control means said gripping shoes will move toward each other to grip said pallet and automatically compensate for any misalignment between said pallet and said truck and thereafter said unloader will operate to remove the load from the pallet.

4. For use with an industrial fork truck for transporting load carrying pallets and having a fluid pressure operated pallet unloader, a pallet gripping device comprising cylinders secured to said truck, a double ended hollow piston slidably disposed in each cylinder, each piston having a partition therein, a flexible fluid pressure conduit connecting the hollow outer ends of each piston, a second flexible fluid pressure conduit connecting the hollow inner ends of each piston, means secured to each piston and carrying pallet gripping shoes and a fluid pressure source and control means connected to said unloader and said flexible conduits whereby upon actuation of said control means said gripping shoes will move toward each other to grip said pallet and automatically compensate for any misalignment between said pallet and said truck and thereafter said unloader will operate to remove the load from the pallet.

5. A gripping device comprising spaced parallel cylinders, a double ended hollow piston slidably disposed in each cylinder, each piston having a partition at substantially the midpoint thereof, a flexible fluid pressure conduit connecting the hollow outer ends of each piston, a second fluid pressure conduit connecting the hollow inner ends of each piston, right and leithand blocks slidably mounted on said cylinders, said righthand block being secured to one piston for movement therewith from an outer position to an inner position beyond the mid-point of the associated cylinder, said leit'nand block being secured to the other piston for movement therewith from an outer position to an inner position beyond the mid-point of the associated cylinder, right and leithand gripping shoes pivotally carried by said blocks, means to bias said shoes in one direction, a fluid pressure source control means connected to said flexible conduits whereby upon actuation of said control means said gripping shoes will move toward each other and automatically compensate for any misalignment between said gripping device and an object to be gripped by said shoes.

6. A gripping device comprising spaced parallel cylinders, a double ended hollow piston slidably disposed in each cylinder, each piston having a partition at substantially the midpoint thereof, a flexible fluid pressure conduit connecting the hollow outer ends of each piston, a second flexible fluid pressure conduit connecting the hollow inner ends of each piston, right and lefthand blocks slidably mounted on said cylinders, said righthand block being secured to one piston for movement therewith from an outer position to an inner position beyond the mid-point of the associated cylinder, said lefthand block being secured to the other piston for movement therewith from an outer position to an inner position beyond the mid-point of the associated cylinder, right and lefthand gripping shoes carried by said blocks and a fluid pressure source and control means connected to said flexible conduits whereby upon actuation of said control means said gripping shoes will move toward each other and compensate for any misalignment between said gripping device and an object to be gripped by said shoes.

7. A gripping device comprising a pair of cylinders a double ended hollow piston slidably disposed in each cylinder, each piston having a partition therein, a flexible fluid pressure conduit connecting the hollow outer ends of each piston, a second flexible fluid pressure conduit connect ing the hollow inner ends or eacn piston, means secured to each piston and carrying gripping shoes and a fluid pressure source and control means connected to said flexible conduits whereby on actuation of said control means said gripping shoes will move toward each other and automatically compensate for any misalignment between said gripping device and an object to be gripped by said shoes, either of said shoes being movable inwardly beyond the mid-point of the associated cylinder to engage and grip a relatively small object positioned to one side of center.

8. A gripping device comprising a pair of cylinders, a double ended hollow piston slidably disposed in each cylinder, each piston having a partition therein, a fluid pressure conduit connecting the hollow outer ends of each piston, a

second fluid pressure conduit connecting the hollow inner ends of each piston, a gripping shoe carried by each piston and a fluid pressure source and control means connected to said flexible conduits whereby upon actuation of said control means said gripping shoes will move toward each other and automatically compensate for any misalignment between said device and an object to be gripped by said shoes, either of said shoes being movable inwardly beyond the mid-point of the associated cylinder to engage and grip a relatively small object positioned to one side of center.

9. A gripping device comprising a pair of cylinders, a double ended hollow piston slidably disposed in each cylinder, each piston having a partition therein, a fluid pressure conduit connecting the hollow outer ends of each piston, a second fluid pressure conduit connecting the hollow inner ends of each piston and a gripping shoe carried by each piston whereby upon the application of fluid pressure to said first conduit said shoes will move toward each other to grip an object and automatically compensate for any misalignment therebetween and said device and upon application of fluid pressure to said second conduit said shoes will move away from each other to release said object, either of said shoes being movable inwardly beyond the mid-point of the associated cylinder to engage and grip a relatively small object positioned to one side of center.

10. A gripping device comprising a pair of cylinders, a double ended piston slidably disposed in each cylinder, a fluid pressure conduit connecting the opposite outer ends of each cylinder, a second fluid pressure conduit connecting the other opposite outer ends of each cylinder, means secured to each piston and carrying gripping shoes and a fluid pressure source and control means connected to said conduits whereby on actuation of said control means said gripping shoes will move toward each other and automatically compensate for any misalignment between said gripping devlce and an object to be gripped by said shoes, either of said shoes being movable inwardly beyond the mid-point of the associated cylinder to engage and grip a relatively small object positioned to one side of center.

11. A gripping device comprising a pair of cylinders, a double ended piston slidably disposed in each cylinder, a fluid pressure conduit connecting the opposite outer ends of each cylinder, a second fluid pressure conduit connecting the other opposite outer ends of each cylinder and a gripping shoe carried by each piston whereby upon the application of fluid pressure to said first conduit said shoes will move toward each other to grip an object and automatically compensate for misalignment therebetween and said device and upon application of fluid pressure to said second conduit said shoes will move away from each other to release said object, either of said shoes being movable inwardly beyond the mid-point of the associated cylinder to engage and grip a relatively small object positioned to one side of center.

JULIAN B. THOMAS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,178,369 Dunham Oct. 31, 1939 2,256,454 Bomar Sept. 16, 1941 2,299,430 Sexton Oct. 20, 1942 2,370,528 Fontaine Feb. 27, 1945 2,371,661 Wilms Mar. 20, 1945 2,390,293 Colson Dec. 4, 1945 2,403,356 Francis July 2, 1946 2,461,877 Brereton Feb. 15, 1949 2,497,118 Ferrario et a1. Feb. 4, 1950 2,508,564 Cardwell et a1. May 23, 1950 2,538,505 Carter Jan. 16, 1951 2,571,550 Ehmann Oct. 16, 1951

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